This invention relates in general to injection molding machines and in particular to a new and useful injection molding machine in which a plasticizer and injector assembly may be positioned for engagement and disengagement from a fixed mold and tool holder part.
The subject of the invention is a plastic injection molding machine with plasticizing and injection group or assembly secured by a press-on and shift means on a fixed injection side tool holder for axial displacement relative thereto.
In plastic injection molding machines, nowadays, the injection group with an injection nozzle of the plasticizing unit is normally pressed with great force onto the sprue bush of the tool in the injection side tool holder usually by a hydraulic press-on device during the injection and after pressing phase, to prevent outflow of liquid plastic between the die and the sprue bush during these phases. In the following dosing phase, the injection group with the plasticizing unit is then separated from the sprue bush by a lift-off stroke of the press-on device, to prevent flow of heat between plasticizing unit and tool.
To ensure good accessibility of the nozzle of the plasticizing unit during maintenance work, the injection group with the plasticizing unit can be retracted into a rear position, and often the injection group and plasticizing unit can even be pivoted out. But to be able to swing out the plasticizing and injection group, the solid connection between press-on and shift means and injection side tool holder or plasticizing and injection group must be undone. The attachment, necessary for axial displacement of the group or for producing the press-on pressure, the attachment, e.g. of the piston rod of the usually provided hydraulic press-on and shift means to the injection side tool holder or to the plasticizing and injection group, is normally effected by means of screws. Since relative to the injection axis of the machine the press-on and shift means must always have at least two press-on and shift means arranged symmetrically to this axis, undoing the attachment always presupposes the unscrewing of a number of screws, which means time ocnsuming and complex manual work.